The composite (plastic) intake manifold may crack near the thermostat housing and cause a coolant leak. Ford released an updated manifold that was reinforced to prevent a recurrence. No recall was issued for this problem but Ford did extend the warranty to seven years on some models from the date of purchase.Google+
Car Problem Reports
Mercury Mountaineer Plastic Intake Manifold May Crack Causing Coolant Leak
Mercury Mountaineer Problem
Electrical & Lights Affected: 4.6L V8
Average Mileage: 126,045 mi (47,000 mi - 209,000 mi)
Visitor, 1999 Mercury Mountaineer, 76,220 mi
Driving down the road, pressed gas pedal and white smoke started coming out back. I pulled over and antifreeze was all over the inside of the engine and hood. Looked and intake manifold where thermostat is housed was completely cracked. It's been leaking for the past month causing antifreeze to cause the ignition coils in cylinder 7 and 8 to go bad. Now it's completely cracked. A shame ford never officially recalled this, poor design that is now costing consumers a hefty bill for a new intake manifold to replace something that wasn't manufactured right to begin with!
Visitor, 2004 Mercury Mountaineer, 100,058 mi
I just purchased this vehicle from a private seller. I saw that it was leaking coolant but got a good price on the mountaineer so purchased it anyway. I took it in to get inspected and had every problem listed on this forum. intake manifold was cracked could not find anywhere but dealer cost 700.00 with labor. It also needed rear bearings and hubs replaced and the back emblem has a crack around it. Total cost to repair all problems 1400.00. That bill should go directly to ford because this is a problem that seems to occur on many of the mountaineers.
Visitor, 2005 Mercury Mountaineer, 108,000 mi
coolant leak at the thermostat. Replaced intake manifold. $850 incl labor. Shame on Ford. This has been a recurring problem since 1997 at least. Eight years of cracking intake manifolds? Quality is job ZERO.
Visitor, 2002 Mercury Mountaineer, 189,000 mi
This problem will cause water to leak into the cylinders and cause them to miss fire making you think there is a problem with the plugs and coils. The car will run horribly but if you look closer you will find that it is in dead the plastic piece under the thermostat housing. It is a real pain. I am still trying to get his fixed and I am sure it is going to cost me a lot of money because it is no longer under warranty.
Visitor, 2002 Mercury Mountaineer, 148,000 mi
I'm purchasing a 2002 mercury mountaineer from a in house financing car dealership and after I drove it for bout a week I noticed the truck started running hot and I finally took it to the shop and they told me that the intake manifold is falling apart because its plastic and its getting to hot and they wanted to charge me around 700 dollars to get it fixed
Visitor, 2002 Mercury Mountaineer
not fixed yet cause i cant afford to at this time
Visitor, 2002 Mercury Mountaineer, 146,000 mi
cracked manifold thermostat housing. Tried to stop the leak with liquid weld--no good. As soon as the car heats up it breaks the welding.
Visitor, 2003 Mercury Mountaineer, 160,000 mi
needs new Intake Manifold gasket. $400 part plus labor. my as well get new thermostat too. $975.
Visitor, 2003 Mercury Mountaineer, 144,677 mi
heater wasn't working. it's at garage right now and they said the manifold is cracked and need to get part from the Ford dealer. Part alone is $441. Going to cost over $800 for total repair. HAVE to get it fixed because it's leaking antifreeze all over inside. This vehicle has cost me thousands since i drove it off the lot brand new. Sooooo frustrated right now. It also needs new brakes and hub bearings, again. Plus i just put 4 new tires on it last month. It's worse than a new car payment.
Visitor, 2002 Mercury Mountaineer, 120,000 mi
heater stopped working and brought attention to low coolant. car was also skipping occasionally. when I inspected engine after adding coolant and getting home I found coolant around spark plug. cause of skip. how did the coolant get there? upon further inspection it looked like it was coming from around thermostat.
I thought a gasket maybe. After removing intake manifold I found the problem was not the gasket but a plastic intake that had broken around thermostat. Expensive and time consuming repair. also replaced plugs and the coil pack on the cylinder where the coolant was leaking. continues to run fine now.